An unexpected interaction between NG-nitro-L-arginine methyl ester and L-arginine in alpha-naphthylthiourea-induced pulmonary oedema in rats

This study was designed to investigate the possible participation of the L-arginine-nitric oxide (NO) pathway in the lung oedema induced by alpha-naphthylthiourea, which is a well-known noxious chemical agent in the lung. Lung oedema was assessed by measuring fluid accumulation in the pleural cavity and the lung weight/body weight ratio following alpha-naphthylthiourea injection. Administration of NG-nitro-L-arginine methyl ester, a NO synthase inhibitor, prior to alpha-naphthylthiourea, produced a significant inhibition of pleural effusion and lung weight/body weight ratio in a dose-dependent manner. L-Arginine, but not D-arginine, when used higher doses (above 300 mg/kg) prior to alpha-naphthylthiourea injection caused a significant inhibition of pleural effusion without altering lung weight/body weight ratio. Lower doses of L-arginine (below 100 mg/kg) did not elicit an inhibitory effect against alpha-naphthylthiourea-induced pulmonary damage. However, lower doses of L-arginine greatly potentiated the inhibitory effect of NG-nitro-L-arginine-methyl ester against alpha-naphthylthiourea-induced lung oedema when used in combination. The interesting aspect of this study is the inhibition by NG-nitro-L-arginine methyl ester, a NO synthase inhibitor, and L-arginine, an endogenous donor of NO, of the lung oedema induced by alpha-naphthylthiourea. The possible role of the L-arginine-NO pathway in lung oedema induced by alpha-naphthylthiourea and the possible underlying mechanisms are discussed.

[Role of membrane protectors and antioxidants in the process of perfusion and preservation of donor lungs]

Comparative study of the effect of four perfusion and preservation solutions on lung function, conducted in experiments on 69 inbred dogs, revealed the following regular features. Euro-Collins and electrolyte solutions cause a marked increase of the capillary-hydrostatic pressure, a significant decrease of colloido-osmotic pressure of the plasma, and, as a result, reduction of the ient between them. This is manifested by edema of the lungs. The use of LPD solution is attended by moderate edema of the lungs in moderately increased capillary hydrostatic pressure and mildly reduced colloido-osmotic pressure of the plasma. Perfusion and preservation of the lungs with the LPD solution, containing membrane protectors and antioxidants, for 12 hours is marked by practically unchanged indices of capillary-hydrostatic pressure, plasma coloido-osmotic pressure, and the gradient between them. Edema of the lungs does not develop in this case.

Angiotensin II-induced pulmonary edema in a rabbit model

We conducted the present study to propose a rabbit model of pulmonary edema (PE) induced by angiotensin II (AII) and to test the preventive effect of losartan on this form of PE. AII was administered to rabbits intravenously at 50, 100, 150 or 300 microg/kg, either by continuous infusion (10 min) or by bolus injection (30 sec). Continuously administered AII (150 microg/kg) induced PE in most cases, while a bolus injection of the same dosage did not. Additionally, the incidence of PE increased with higher dosages of AII when it was infused continuously. A newly established parameter, the area under the systolic blood pressure-time curve corrected by baseline (cAUC), was prone to rise as the incidence of PE increased. Moreover, cAUC signficantly correlated with the wet-dry lung weight ratio (r=0.66, P<0.05). Subsequently, 0.5 or 3.0 mg/kg of losartan was given before continuous infusion of 150 microg/kg of AII. The higher dosage of losartan prevented PE completely, while the lower one did so moderately. We concluded that intravenous administration of AII induces PE, probably as a result of increasing afterload. Furthermore, an adequate dosage of losartan can prevent PE because it reduces the pressor effect of AII.

Anti-inflammatory 17beta-thioalkyl-16alpha,17alpha-ketal and -acetal androstanes: a new class of airway selective steroids for the treatment of asthma

The synthesis and anti-inflammatory potencies of a new class of 17beta-thioalkyl-16alpha,17alpha-ketal and -acetal androstanes are described. This new class of steroids was made by fragmentation of 2-thioxo-1,2-dihydropyrid-1-yl esters of the corresponding 17-acids to the 17-radical. The radical generated was trapped using a variety of radicophilic disulfides, giving a steroidal D-ring having acetal or ketal functionality at C-16 and C-17, together with a sulfide link at C-17. Compounds from this series bind to the glucocorticoid receptor with high potency and are functional agonists as measured by their ability to induce tyrosine aminotransferase activity in a rat hepatic cell line in vitro. These 17beta-thioalkyl androstanes potently inhibit Sephadex-induced rat lung inflammation when administered directly into the airways. The high topical potency, together with a low propensity to induce systemic glucocorticoid-like side effects (rat thymus involution), provides the present compounds with a high degree of airway selectivity compared with currently available inhaled glucocorticoids. The presently described 17beta-thioalkyl-16alpha,17alpha-ketal androstanes may be useful for therapies for inflammatory diseases such as asthma.

Pulmonary edema induced by phorbol myristate acetate is attenuated by compounds that increase intracellular cAMP

We have investigated the effect of terbutaline, aminophylline and dibutyryl cyclic AMP (DBcAMP) on phorbol myristate acetate (PMA)-induced acute lung injury in isolated, blood-perfused rabbit lungs. Pulmonary arterial pressure and lung weight were measured for 30 min after a bolus injection of PMA (10 mu g/kg). In the group exposed to PMA alone, the mean pulmonary arterial pressure (PAP) increased from 16.33 + or - 1.28 to 77.30 + or - 6.40 mmHg (P <0.001), and lung weight increased by 70.69 + or - 10.94 g during the 30 min after PMA challenge (P<0.001). Pretreatment with terbutaline, aminophylline or DBcAMP prevented the increases in both PAP and lung weight (P <0.001). Each of the three drugs also prevented the increase in pulmonary vascular permeability induced by PMA: terbutaline, aminophylline, and DBcAMP all significantly reduced the pulmonary capillary filtration coefficient (KfC) as well as the albumin concentration in the lung lavage fluid after PMA exposure. Post-treatment with terbutaline 5 min after PMA administration also had a protective effect. The mechanisms responsible for these protectivp3 effects may all involve an increase in intracellular cAMP, since all three drugs increase cAMP in the lung (though by different mechanisms). Our data further indicate that the inhibition of tumor necrosis factor production may likewise play an important role in the protective effect exerted by these drugs.

In-line leukocyte filtration during bypass. Clinical results from a randomized prospective trial

Leukocyte mediated pulmonary injury may delay recovery after cardiac surgery, and leukocyte depletion during bypass has been suggested. Two groups of patients were randomly, prospectively assigned from 50 sequential patients to undergo open heart surgery using cardiopulmonary bypass, either with (n = 25) or without (n = 25) leukocyte filters. The two groups were not significantly different regarding age, gender, race, pre-operative ejection fraction, pump time, or cross-clamp time. Post operative arterial blood gases (pO2: 173 +/- 66 vs 192 +/- 107; pCO2: 30.2 +/- 8.2 vs 30.8 +/- 8.0), pulmonary vascular resistance (PVR 105 +/- 45 vs 112 +/- 50 dyne cm-5), time on ventilator (17.8 +/- 6.4 vs 19.7 +/- 8.6 hr), and length of hospital stay (7.65 +/- 4.57 vs 8.52 +/- 5.87 days) were not different between groups (mean +/- SD, with vs without filters, respectively). Arterial oxygenation was somewhat poorer, and PVR was somewhat lower in the leukocyte filtered group. However, these trends did not produce significant decreases in total ventilator time or length of hospital stay. In-line filtration did remove leukocytes, but did not reduce circulating leukocyte count. In effect, leukocyte filtration produced an effective leukocyte concentration at the filter site. These data do not support routine incorporation of in-line leukocyte filtration during bypass.

Protective effects of BQ-123, an ETA receptor antagonist, against leukotoxin-induced injury in rat lungs

We tested the hypothesis that BQ-123, a novel endothelin type A (ETA) receptor antagonist, protects the lung against leukotoxin 9,10-epoxy-12-octadecenoate (Lx), which causes acute lung injury in animals. In isolated rat lungs perfused with Earle's balanced salt solution, BQ-123 suppressed the Lx-induced increase in wet lung weight, wet lung weight/dry lung weight, the effluent perfusate lactic dehydrogenase activity, and effluent perfusate and lung tissue ET-1 levels. BQ-123 also significantly attenuated the Lx-induced increase of the pulmonary capillary filtration coefficient. Thus our experimental results indicate that the ETA receptor antagonist, BQ-123, protects against Lx-induced experimental lung vascular injury.

Aerosolized specific antibody protects mice from lung injury associated with aerosolized ricin exposure

Parenteral vaccination with ricin toxoid, although protective against death after a lethal aerosol ricin challenge, only partially protects against lung lesions. Therefore, we tested whether passive protection with aerosolized specific anti-ricin IgG (goat polyclonal, affinity-purified) could protect against both lethality and lung lesions in unvaccinated mice. Healthy CD-l mice were administered antibody (Ab) by small particle aerosol. Group 1 received non-specific control Ab (2160 mg/min/m3), and groups 2 and 3 received anti-ricin IgG (960 and 3280 mg/min/m3, respectively). Each group was challenged with a lethal dose of aerosolized ricin 1 hr after Ab exposure. All group 1 (control Ab) mice developed diffuse airway epithelial necrosis, with severe interstitial edema and inflammation involving all lung lobes, and died 48-96 hr post-challenge (PC). In contrast, in groups 2 and 3 at 24 hr PC, lung lesions were absent to very mild although there was rare epithelial necrosis in the upper airways in both groups. By 48 hr PC, necrosis of the tracheal epithelium and peritracheal inflammation were noted in some group 3 mice only. By 4 days PC, lungs and airways did not differ from cage controls in most group 2 and 3 mice. Weight gain in group 2 and 3 mice paralleled that of control mice. At 14 days PC, lungs were no different in controls than in group 3 mice. However, two non-survivors in group 3 had obstructions due to proximal airway epithelial damage. All group 2 mice survived, although a mild lymphoplasmacytic perivasculitis was present at 14 days PC which was not noted in the group 3 mice.

Keratinocyte growth factor attenuates lung leak induced by alpha-naphthylthiourea in rats

OBJECTIVE

To investigate the effect of pretreatment with keratinocyte growth factor on acute permeability pulmonary edema.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Specific pathogen-free Sprague-Dawley rats.

INTERVENTION

Acute permeability pulmonary edema was induced with an injection of alpha-naphthylthiourea, and lung leak was assessed in an isolated perfused lung model over 180 mins. Leak was confirmed with wet/dry lung weight ratios, and the alveolar fluid protein concentration was measured after bronchoalveolar lavage. The effect of pretreatment with keratinocyte growth factor (injected intratracheally 48 hrs before the experiment) on alpha-naphthylthiourea-induced pulmonary edema was assessed (keratinocyte growth factor/alpha-naphthylthiourea group). Control groups (Control and keratinocyte growth factor/Control) were also studied. Histopathology was performed for each of the four groups.

MEASUREMENTS AND MAIN RESULTS

The alpha-naphthylthiourea produced an acute permeability pulmonary edema detected by lung leak over the 180-min ex vivo period of monitoring the isolated perfused lung (leak = 8+/-mL; wet/dry weight ratio 14.7+/-2; lavage protein 3.1+/-1 mg/mL). Pretreatment with keratinocyte growth factor significantly attenuated these parameters (leak = 2.3+/-0.4 mL; wet/dry weight ratio 7.1 +/- 0.5; lavage protein 0.28 +/-0.03 mg/mL), which were not significantly different from the control group and the keratinocyte growth factor/control group. Histopathology showed abundant type II pneumocyte hyperplasia in the lungs of animals pretreated with keratinocyte growth factor, and marked pulmonary edema in animals pretreated with alpha-naphthylthiourea. Less edema was apparent in the keratinocyte growth factor/alpha-naphthylthiourea group. All data are expressed as mean +/- SEM.

CONCLUSIONS

Pretreatment with keratinocyte growth factor significantly attenuates pulmonary edema induced by alpha-naphthylthiourea. The mechanisms of this protection are likely related to type II pneumocyte hyperplasia, but remain to be specifically elucidated.

Excitotoxicity in the lung: N-methyl-D-aspartate-induced, nitric oxide-dependent, pulmonary edema is attenuated by vasoactive intestinal peptide and by inhibitors of poly(ADP-ribose) polymerase

Excitatory amino acid toxicity, resulting from overactivation of N-methyl-D-aspartate (NMDA) glutamate receptors, is a major mechanism of neuronal cell death in acute and chronic neurological diseases. We have investigated whether excitotoxicity may occur in peripheral organs, causing tissue injury, and report that NMDA receptor activation in perfused, ventilated rat lungs triggered acute injury, marked by increased pressures needed to ventilate and perfuse the lung, and by high-permeability edema. The injury was prevented by competitive NMDA receptor antagonists or by channel-blocker MK-801, and was reduced in the presence of Mg2+. As with NMDA toxicity to central neurons, the lung injury was nitric oxide (NO) dependent: it required L-arginine, was associated with increased production of NO, and was attenuated by either of two NO synthase inhibitors. The neuropeptide vasoactive intestinal peptide and inhibitors of poly(ADP-ribose) polymerase also prevented this injury, but without inhibiting NO synthesis, both acting by inhibiting a toxic action of NO that is critical to tissue injury. The findings indicate that: (i) NMDA receptors exist in the lung (and probably elsewhere outside the central nervous system), (ii) excessive activation of these receptors may provoke acute edematous lung injury as seen in the "adult respiratory distress syndrome," and (iii) this injury can be modulated by blockade of one of three critical steps: NMDA receptor binding, inhibition of NO synthesis, or activation of poly(ADP-ribose) polymerase.

Esmolol aids extubation in intensive care patient with ischaemic pulmonary oedema

A 49-year-old man with a history of ischaemic heart disease failed successful tracheal extubation on four consecutive occasions following emergency surgery because of the development of acute pulmonary oedema. Attenuation of the cardiovascular responses to tracheal tube removal by pretreatment with an intravenous infusion of esmolol hydrochloride allowed successful extubation of the patient to be achieved.

Effects of University of Wisconsin and Euro-Collins solutions on interstitial pulmonary edema in isolated rat lungs

Macromolecules are present in lung preservation solutions to limit liquid filtration out of the pulmonary circulation and minimize pulmonary edema. We tested the effectiveness of these molecules by measuring interstitial edema in rat lungs perfused with macromolecular solutions (University of Wisconsin [UW] solution and Euro-Collins solution supplemented with modified pentastarch [pentafraction, PEN]) or with solutions that lacked macromolecules (UW solution with PEN and Euro-Collins solution.) The lungs were inflated with air and perfused with one of the test solutions, then rapidly frozen and prepared for histological analysis. From tissue sections, we measured cross-sectional areas of pulmonary arteries and veins, and also measured cross-sectional areas of the interstitial spaces surrounding arteries and veins. We then calculated the interstitium-to-vessel cross-sectional area ratio. In lungs perfused with macromolecular solutions these ratios were 0.09+/-0.15 and 0.53+/-0.56 (mean +/- SD) for UW solution and Euro-Collins solutions solution with PEN, respectively (P</=0.05). In lungs perfused with solutions that lacked macromolecules, area ratios were 0.48+/-0.88 and 1.95+/-1.82 for UW solution without PEN and Euro-Collins solution, respectively (P</=0.05). Solutions containing PEN caused less interstitial expansion than their counterparts that lacked it, but UW solution without PEN caused interstitial expansion equal to that of Euro-Collins solution with PEN. We conclude that macromolecules limit edema formation, but other constituents of UW solution limit edema formation also.

Effects of furosemide, torasemide and controlled fluid intake on perfluoroisobutene induced lung oedema and mortality

Permeability type lung oedema has been induced in rats by exposing them to the lung oedemagen perfluoroisobutene (PFIB). The loop diuretic furosemide (CAS 54-31-9) reduces the lung oedema and the pattern and severity of the pathological changes associated with inhalation of PFIB (mean Ct 945 mg.min.m-3) and delays the time to death following inhalation of an LCt65 equivalent of the gas. Combined administration of the loop diuretic torasemide (CAS 56211-40-6) and water deprivation reduces PFIB induced oedema and mortality during the treatment period (24 h). Controlling the intake of fluids after treatment prevents the rapid increase in oedema and mortality which occurs when water is returned ad libitum. Torasemide and water deprivation followed by controlled fluid intake delays but does not reduce the overall mortality due to an LCt70 of PFIB.

Effect of eicosanoid inhibition on the development of pulmonary edema after acute lung injury

In experimental models of acute lung injury, cyclooxygenase inhibition improves oxygenation, presumably by causing a redistribution of blood flow away from edematous lung regions. This effect on perfusion pattern could also reduce alveolar edema formation. On the other hand, pulmonary pressures usually increase after cyclooxygenase inhibition, an effect that could exacerbate edema accumulation. Therefore we tested the following hypothesis: the total accumulation of pulmonary edema in dogs during a 24- to 28-h period of observation after acute lung injury caused by oleic acid will be less in a group of animals treated with meclofenamate (n = 6) or with the thromboxane-receptor blocker ONO-3708 (n = 5) than in a group of animals treated with oleic acid alone (placebo, n = 6). Lung water concentrations (LWC), the regional pattern of pulmonary perfusion, and protein permeability were measured with the nuclear medicine imaging technique of positron emission tomography. After 24-28 h, LWC was significantly less (P < 0.05) in the ONO-3708 group than in the meclofenamate group (a similar trend was seen compared with the placebo group, P = 0.12). After 24-28 h, pulmonary arterial pressures were highest in the meclofenamate group. Regardless of group, the only significant correlation with the change in LWC was with the integral of pulmonary pressures over the 24- to 28-h period. The data suggest that thromboxane inhibition will reduce edema accumulation in acute lung injury but that this effect depends on reducing as much as possible the simultaneous development of pulmonary hypertension from other causes.

Cardiac failure aggravated by timolol eye drops: preoperative improvement by changing to pilocarpine

A 73-year-old woman with cardiac dysfunction had several episodes of severe bradycardia and pulmonary oedema when waiting for peripheral vascular surgery. She used timolol eye drops for primary open-angle glaucoma. The first episode of pulmonary oedema occurred two weeks prior to and the second on the day before the planned surgery. There were another two episodes of pulmonary oedema before she was transferred to the Department of Internal Medicine where she had a further two episodes of cardiac failure. After changing timolol to pilocarpine eye drops, the patient's condition was stabilized, and two weeks later surgery and postoperative recovery were uneventful.

Glutathione supplements protect preterm rabbits from oxidative lung injury

The main objective of this study was to determine if glutathione (GSH) supplementation attenuated hyperoxic lung injury. Preterm (29 days) rabbits were delivered and exposed for 24 h to 1) room air, 2) room air and GSH, 3) 95% oxygen and GSH. GSH supplements (1 mM) were delivered in the nutritional support of 10% dextrose and saline through a peritoneal catheter. Animals assigned to oxygen had decreased lung volumes at 35 cmH2O, decreased lung compliance, increased edema, decreased cell viability, and decreased lung tissue and lavage-reduced/oxidized GSH levels, compared with control animals. Despite exposure to hyperoxia, animals supplemented with GSH were not different from room air controls with respect to lung mechanics, edema, cell viability, or tissue and lavage GSH. These studies suggest that GSH supplementation maintains normal lavage and lung tissue GSH levels in preterm animals exposed to hyperoxia and attenuates the changes in lung mechanics associated with oxygen-induced lung injury.

Prevention of OKT3 nephrotoxicity after kidney transplantation

In our experience the use of OKT3 as prophylaxis in renal transplantation has been associated with an increased incidence of both delayed graft function and thromboses of graft vessels. OKT3 nephrotoxicity might have been favored by restriction of perioperative fluid infusion to prevent pulmonary edema and by the use of very high dose (30 mg/kg) of methylprednisolone (mPDS) before the first OKT3 injection to reduce the release of cytokines. This led us to modify our perioperative management in three ways: (1) hydration status was optimalized; (2) the calcium-channel blocker diltiazem, considered beneficial for recovery of graft function, was administered on the day of transplantation; and (3) the dose of mPDS given before the first OKT3 injection was fixed at 8 mg/kg. Comparison of two consecutive series of patients (group 1, control patients, N = 172; group 2, managed as described above, N = 173) showed that: (1) the incidence of delayed graft function fell from 52% in group 1 to 22% in group 2 (P < 0.0001): (2) the incidence of pulmonary edema was not significantly increased in group 2 (3.5% vs. 1.7% in group 1, P = 0.5); and (3) the frequency of intragraft thrombosis fell from 7.6% in group 1 to 1.2% in group 2 (P = 0.0034). Multivariate analysis showed that the volemia/diltiazem program and avoidance of high mPDS dose were the most important factors responsible for the reduced occurrence of delayed graft function and graft vessels thrombosis, respectively. We conclude that a combined strategy of appropriate dosage of steroids before the first OKT3 injection, administration of a calcium-channel blocker and optimalization of volemia is safe and efficiently prevents against OKT3 nephrotoxic effects.

[Postpneumonectomy pulmonary edema. Review of the literature. Apropos of 2 new cases]

Postpneumonectomy pulmonary edema is a poorly understood clinical entity. We report two new cases and review the literature. The main manifestations are increased pulmonary perfusion flow, endothelial damage, and amputation of the lymphatic system. Treatment depends on the physiological situation of the lung remaining after pneumonectomy. Prevention requires co-operation between the medical and surgical teams.

The lungs in immature infants: how important is surfactant therapy in preventing chronic lung problems?

Seventy-five premature infants weighing between 600 and 3200 g were studied over a period of 1 year. All of the infants received surfactant therapy for hyaline membrane disease immediately after birth and, thereafter, up to four doses every 6 h. The roentgenographic findings in all patients were documented at birth and at 2 days, 7-10 days, and 21-28 days of life. Larger babies responded to surfactant therapy better than did smaller infants. The smaller infants, even after initial clearing, were prone to develop pulmonary edema and the bubbly lungs of bronchopulmonary dysplasia. These data suggest that small infants, while initially responding to surfactant therapy with clearing of their lungs, are still at considerable risk of developing chronic lung disease in the form of pulmonary edema and bronchopulmonary dysplasia. An explanation is offered for why this occurs; at the same time it is suggested that, in view of our findings and those in the literature, the problems of pulmonary edema and bubbly lungs be more clearly separated.

[Hypertensive crises]

The goal of the accurate treatment of an hypertensive crisis is to reduce the critically elevated blood pressure to a safer level, in an hemodynamic point of view, although not necessarily normal. The authors stress that a prompt and correct diagnosis in distinguishing hypertensive emergencies from urgencies, in understanding its pathophysiology and the knowledge of available drugs is essential for a successful management.

Beneficial effects of a leukotriene receptor antagonist on thrombin-induced pulmonary edema in the rat

The effect of a selective leukotriene receptor antagonist, the peptide ICI 198,615, on thrombin-induced pulmonary edema was studied in rats. Administration of thrombin produced a significant increase in lung weight (p < 0.05), wet weight to dry weight ratio (WW/DW; p < 0.05), and relative lung water content (p < 0.05). These increases were all significantly reduced (p < 0.05) by ICI 198,615 (bolus 15 mg/kg, infusion 15 mg/kg/h). Thrombin infusion caused a significant increase in myeloperoxidase activity in the lung tissue (p < 0.05). This increase was further accentuated by ICI 198,615, indicating that the effect of this antagonist is not due to reduction of leukocyte infiltration in the lungs. The results thus show that a leukotriene receptor antagonist effectively counteracts the increase in lung vascular permeability to protein caused by thrombin, and indicate that leukotrienes are important mediators of thrombin-induced pulmonary edema in the rat.

NG-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthesis, ameliorates interleukin-2-induced capillary leak syndrome in healthy mice

We tested whether NG-nitro-L-arginine methyl ester (L-NAME), a potent inhibitor of NO synthesis, can prevent interleukin-2 (IL-2)-induced capillary leakage. Healthy C3H/HeJ female mice were treated with: nothing; IL-2 (10 injections; 35,000, 15,000, or 7,500 Cetus U i.p. every 8 h); IL-2 + L-NAME (0.01, 0.1, 0.5, and 1 mg/ml of drinking water starting 1 day before IL-2 therapy and ending with IL-2 therapy); or L-NAME alone. In the first series of experiments, mice were killed 1 h after last IL-2 injection to measure pleural effusion, and water content of the lungs, spleen, and kidney (markers of capillary leakage), as well as NO2- + NO3- levels in the serum and pleural effusion. In the two additional series, the survival of treated mice was followed. All doses of IL-2-induced capillary leak syndrome as indicated by pleural effusion, pulmonary edema, and fluid retention in the spleen and kidney. NO production was positively correlated with manifestation and severity of this syndrome. NO2- + NO3- levels in the pleural effusion were directly related to IL-2 dose, and L-NAME treatment reduced both the NO production and severity of capillary leakage, excepting fluid retention in the kidney. However, L-NAME therapy prevented IL-2-induced mortality only when combined with a middle range IL-2 dose (15,000 U/injection). In summary, oral L-NAME therapy effectively prevented IL-2-induced capillary leakage in healthy mice, suggesting its potential value as a supplement in IL-2-based immunotherapy of cancer and infectious diseases.